1. Field of the Invention
The invention is generally related to laying pipeline in deep water and more particularly to the recovery of pipeline in deep water.
2. General Background
During the course of pipe laying in deep water, the possibility of having to deal with buckled lines, damaged lines, or other instances where there is a need to recover the pipe exists. Normally, some kind of an attachment, so called head/hook, is attached to one end of the pipe for abandonment or recovery purposes. It is possible, however, that the head of the pipe may be damaged during the pipe laying operations or buried in the sea floor. In either case, the pipeline is retrieved with an emergency recovery tool.
The inventors are aware of a pipeline recovery tool designed by Oil States/Hydro Tech for twelve and three quarter inch pipe and eighteen inch diameter pipeline sizes. This device is made out of forged and machined pieces of steel. Forging and machining are expensive processes and require special machines and procedures and needs a long lead time for fabrication.
The current state of the art leaves a need for pipeline emergency recovery tools.
Pipelines in deep water are installed, in many instances, through a process that utilizes collars rigidly fixed to the pipeline at regular intervals. These collars embody various designs such as a short, heavy wall section of pipe with an xe2x80x9cupsetxe2x80x9d or land at each end, as well as a short heavy wall section which includes an external ring. These collars function as buckle arrestors to inhibit buckle propagation along the pipeline. Collars are also used to facilitate pipeline installation, as they allow handling of pipe segments during pipe lay operations.
The invention addresses the above need. What is provided is a pipeline recovery tool that engages a collar on the pipeline at the desired location and recover the pipeline and reduces the material and fabrication costs of building such equipment. Instead of forging and machining, the tool is made from steel plates welded together. The rigged-up tool is lowered over the pipeline and engaged with the pipeline such that a fixed claw engages the collar on the pipe. An ROV is used to release a movable dog on the tool that engages the collar and then locks the fixed claw in position. The rigging on the fixed claw side of the tool is released. The pipeline is then lifted to the surface by a lift arm on the first end of the tool.